I like to think this just means that James Shields has learned some things over the course of his career that bode well for his future.

Basically, yes. Learning something/adjusting/change in approach all mean the same thing.

He went from being primarily a 4-seam, two-seam fastball guy who mixed in changeups to being a guy who throws his 4-seam fastball and changeup at nearly identical rates, and uses his breaking pitches much more than previously.